Serial Position Effect Lab

We've talked about the different "types" of memory - but how can we show that they're different empirically. In this lab, you'll be learning about the serial position effect and investigating how to manipulate it.

Experiment 1

Go to: http://psych.hanover.edu/JavaTest/CLE/Cognition/Cognition/serialposition_instructions.html (JAVA REQUIRED - chrome users you can get an extension if you really want to do this. Otherwise try a different browser)

Scroll to bottom of page and click "Click here to star the experiment"

Use these settings when the experiment window pops up:

Number of conditions to test: 1

Stimuli types for each condition: long words

Number of times list is repeated: 5

Number of items in list: 10

Duration of each item: 4

Time before recognition: 0

Time for recognition: 15

Font size: 24

Duration of fixation target before block: 1

Click "done" to begin the experiment

When you finish, the program will give you a summary of the data which looks like this:

The numbers after P(Recog) represent the average proportion of times you remembered the right word for each position (1-10). For example, the average proportion I recalled the 1st word in each trial was 0.20 or 20%. (Note: These numbers might look very different from yours, I ran this with a few settings changed and...wasn't paying attention).

Take your results and graph them with the position (1-10) as the x-axis, and proportion (or convert to %) as the y axis. Mine would look like this:

Before scrolling past this, look at your graph. What do you notice about it's shape? At what positions to we remember words better?

Did your graph look something like this?

This is the serial position curve! Notice it's u-like shape. You remember items better when they are presented early in the list OR late in the list.

There are two key features of this curve known as the primacy effect and recency effect.

The primacy effect refers to items at the beginning of the list being recalled better than items in the middle. It's highlighted on the left side of the image below.

The recency effect refers to items at the end of the list being recalled better than items in the middle. It's highlighted on the right side of the image below.

Researchers hypothesized that the primacy effect was due to long-term memory, and the recency effect was due to short-term memory. The first items on the list enter long-term memory because they can be processed more than other items on the list. The last items on the list remain in short-term memory since they were just seen before recall.

Dissociating Short-Term and Long-Term Memory

While the explanation of the of the serial position effect due to the stores of short-term and long-term memory might make sense, researchers needed evidence to show that the two were actually different. They needed to dissociate short-term and long-term memory. To do this, they had to cleverly alter the design of the experiment to eliminate the primacy effect, but NOT the recency effect and vice versa. But I'M not going to tell you how they did this. Instead, you're going to try some hypotheses yourself!

Experiments 2-3 (or however many you have time for)

Go to the same website before and start the experiment

Change ONE of the settings from the original experiment you did that you think may eliminate the primacy or recency effect.

These are the settings from last time. I've highlighted some things you might try:

Number of conditions to test: 1

Stimuli types for each condition: long words

Number of times list is repeated: 5

Number of items in list: 10

Duration of each item: 4

Time before recognition: 0